Ribbed pipe unit

ABSTRACT

The production of ribbed heating pipes and ribbed pipe units in which ribs consisting of plates of sheet metal which are provided with recesses of a size and shape in accordance with that of the outer surface of the core pipe or pipes are applied tightly upon the latter so as to project radially therefrom. The edges of these recesses in the rib plates are additionally provided with grooves. A metal, for example, aluminum, is then cast in a suitable mold between the adjacent rib plates so as to form jacket sections around the core pipe in which the rib plates are embedded. This metal also penetrates through and fills out the grooves in the edges of the apertures of the rib plates and thereby connects the adjacent jacket sections to each other.

Elite States Schiill tet [54] RIBBED PIPE UNIT [72] Inventor: Giinter Scholl, Casa Rosina, 6549 Pianezzo/Pando, Switzerland [22] Filed: June 4, 1970 [21] Appl. No.: 43,534

[30] Foreign Application Priority Data June 13, 1969 Germany ..P 19 30 040.4

July 31, 1969 Germany ..P 19 38 928.7

Feb. 16, 1970 Germany ..P 20 06 893.3

[52] US. Cl. ..165/180, 29/1573, 165/151, 165/181, 165/182, 285/137 R, 285/284,

. 285/289 [51] Int. Cl. ..F28f 21/00 [58] Field of Search..285/l37 R, 187, 284, 288, 289; 165/180, 181, 182, 151; 29/1573 A, 157.3 C, 157.3 B; 164/111 1 Aug. 29, 1972 2,400,157 5/1946 Merry ..165/182 X 3,004,328 10/1961 Pepper et a1 ..165/182 X 3,208,776 9/1965 Buschow ..285/284 FOREIGN PATENTS OR APPLICATIONS 588,712 12/1959 Canada ..165/181 1,392,332 2/1965 France ..165/181 66,793 1/1893 Germany ..165/180 Primary Examiner-Dave W. Arola Att0rney-Karl F. Ross [5 7] ABSTRACT The production of ribbed heating pipes and ribbed pipe units in which ribs consisting of plates of sheet metal which are provided with recesses of a size and shape in accordance with that of the outer surface of the core pipe or pipes are applied tightly upon the latter so as to project radially therefrom. The edges of these recesses in the rib plates are additionally provided with grooves. A metal, for example, aluminum, is then cast in a suitable mold between the adjacent rib plates so as to form jacket sections around the core pipe in which the rib plates are embedded. This metal also penetrates through and fills out the grooves in the edges of the apertures of the rib plates and thereby connects the adjacent jacket sections to each other.

8 Claims, 24 Drawing Figures PAIENIEDMIBZQ I912 3.687.194

SHEET 1 OF 6 INVENTOR ATTORNEY PATENTEDAUBZQ 1972 SHEEI 2 BF 6 Gi'INTER JQHEJLL INVENTOR ATTORNEY P'A'TE'NTEDMIBZ m2 3.687; 1 94 SHEET 3 OF 6 GUNTER scH'c'mL INVENTOR ATTORNEY PATENTEDmszs 1972 3.687; 194

sum u 0F 6 GUNTER SCH'OLL INVENTOR ATTORNEY PATENTEDwczs m2 3 687, 1- 94 sum 5 or e GUNTZJR so HOLL INVENTOR ATTORNEY PATENTEDwazs m2 sum 6 or 6 GUNTER scli'ciLL INVENTOR arasnp PIPE UNIT FIELD OF THE INVENTION The present invention relates to a method of producing ribbed heating pipes the ribs or rib sections of which are provided with apertures or recesses of a size and shape in accordance with those of the core pipe or pipes and are connected to each core pipe so as to be in good heat conduction therewith by means of a metal which is cast in a liquid condition between them and is then cooled.

BACKGROUND OF THE INVENTION There are numerous methods known for producing ribbed heating pipes on which the ribs are conductively connected to the core pipe and extend transverse to its longitudinal axis. Apart from the known method of producing such ribbed heating pipes by winding straight or corrugated metal strips around the outer surface of the core pipe, it is probably the most conventional method to punch the ribs out of sheet metal and to secure them to the core pipe. These ribs may be punched out so as to have an aperture or neck in accordance with the outer shape and diameter of the pipe so as to permit them to be slipped successfully over the pipe. A mechanically solid and heat-conductive connection between the pipe and the slipped-on ribs may be attained by dip-coating in zinc. Such ribs may also be connected to the core pipe by welding them individually thereto either electrically or by autogenous welding which may be done more or less automatically on special machines. At least for heating pipes for lower temperatures it is also possible to attain a mechanically secure and heat-conductive connection between the pipe and its rib by expanding the pipe either mechanically or hydraulically.

According to still another known method of producing ribbed heating pipes, each rib consists of two or more sections which are then connected by electric butt-welding to a core pipe or even to several core pipes simultaneously. The ribbed pipes which are produced according to this method are usually employed only for very particular purposes especially because of their high cost of production.

OBJECT OF THE INVENTION It is an object of the present invention to provide ribbed pipes of the type as first described above which are designed so as to insure that a good mechanical and heat-conductive connection will be attained between the ribs and the core pipe or pipes and the ribbed pipes may also be produced in a very simple manner and at a very low cost.

SUMMARY OF THE INVENTION The present invention for attaining this object consists in providing the edges of the apertures or recesses in the ribs or rib sections which engage with the outer peripheral surface of a core pipe with shallow grooves, for example, of a dovetailed or other shape which form channels between the opposite sides of the ribs. Another feature of the invention consists in connecting the ribs to the core pipe by casting a metal between the adjacent ribs so as to form a jacket around the core pipe in which the ribs are embedded. In this casting operation, the liquid metal also penetrates through and fills out the groovelike channels in the ribs or rib sections and thus connects the adjacent sections of the jacket at both sides of each rib to each other. Therefore, when this metal has cooled, the ribs or rib sections will be rigidly secured to the core pipe by the jacket sections at both sides of each rib or rib sections and also by the metal which fills out the groovelike channels and integrally connects these adjacent jacket sections to each other.

Such a ribbed pipe according to the invention may consist of an individual core pipe and the ribs thereon, but the invention also results in a ribbed pipe unit which consists of a plurality of core pipes which preferably extend parallel to each other and are connected to each other by the ribs or rib sections which extend transversely to all of the core pipes. I also design the mold in which the casting operation is carried out for connecting the ribs or rib sections to the core pipe or pipes so that in the same operation radially extending fins or finlike projections are cast on the jacket which project from both sides of each rib or may connect the adjacent ribs to each other by extending in the longitudinal direction of the core pipe and at suitable distances from each other. If each of the ribs consists of a pair of plates in alignment with each other, and each of these plates has one edge which abuts against the corresponding edge of the other plate and is provided with a semicircular aperture the edge of which engages with the core pipe and is provided with the mentioned groovelike channels, the invention further provides that two diametrically opposite fins or finlike projections extending radially from the core pipe along the abutting edges of the two rib plates and thus also connects these edges to each other. If desired, these abutting edges of the two plates forming one rib may be further provided with grooves in corresponding positions, for example, of a dovetailed shape, which during the casting operation will likewise be filled out with the casting metal for further improving the connection between the fins or finlike projections and the two plates which together form one rib and also the connection between these two plates.

If the core pipe and the jacket which is cast around it consist of two different materials and the material of the jacket has a higher coefficient of thermal expansion than the material of the core pipe, the difficulty arises that, although the jacket when in a cold condition is shrunk tightly upon the core pipe, it may slightly separate in radial directions from the core pipe when both of them are heated so that the jacket would then not be in positive thermal contact with the core pipe.

To insure a positive thermal contact between the core pipe and the jacket when heated, despite the different coefficients of thermal expansion of the materials of these two elements, I provide that annular grooves are cut at suitable distances from each other into the outer wall surface of the core pipe or that, in place of such grooves, a continuous screw thread is cut into this surface. These annular grooves or this screw thread should be provided with flanks which extend substantially at right angles to the longitudinal axis of the core pipe. This has the advantage that, when the jacket expands more than the core pipe and disengages slightly from the latter in radial directions, the flanks of the annular grooves or of the screw thread will remain in direct contact with the corresponding flanks of the annular grooves or of the screw threads which are molded into the jacket surrounding the core pipe. Thus, a large surface area of the core pipe and of the jacket will remain in tight and heat-conductive engagement with each other.

A preferred method of producing a ribbed pipe according to the invention comprises the steps of inserting the core pipe into a continuous channel which is formed between two mold sections when they are moved against each other, inserting rib plates in the form of equal pairs from the outside into the two mold sections through slots which are provided in these sections by pressing these pairs of rib plates from the opposite sides by means of a pair of press plungers tightly against the outer surface of the core pipe and against each other, then casting the metal through a plurality of channels within the mold into the cavities remaining in the mold, and, after the casting metal has cool-ed, drawing the two mold sections away from each other and thus also from the finished ribbed pipe so that the latter may be removed from the mold.

This method of production may be employed very economically for manufacturing ribbed pipes on which the rib plates are spaced not less than approximately mm from each other. If, however, the rib plates are to be spaced at still smaller distances from each other, the deformations of the mold sections which are caused by the heating and cooling thereof reduce the service life of such a mold to such an extent that it may be no longer economical.

In order to permit an economic production also of ribbed pipes with core pipes either of a circular or flat cross section and with ribs or rib plates which are only spaced at a distance of approximately 1 mm from each other, the present invention further provides that the ribs or rib sections are stacked on each other so that the adjacent ribs or rib sections of the stack are separated by subsequently removable spacing strips, that the core pipe or core pipes are inserted into the channel-like spaces of this stack which are formed by the apertures in the ribs and spacing strips, that thereafter the metal is cast into the spaces remaining at the inside of the stack, and that, after the casting metal has cooled and the ribs or rib sections are secured by this metal to the core pipe or pipes, the spacing strips are again withdrawn from the ribs.

If according to the inventive method a ribbed pipe unit is to be produced which is especially suitable for being employed as an engine radiator for an automobile, the rib plates are preferably bent at z-shaped angles adjacent to the edges of their recesses facing the core pipes. Each z-shaped web of each rib plate and the arm which is connected thereto then forms together with the corresponding arm of the adjacent rib plate an open casting channel which is open toward the core pipe and connected by the grooves in the wall of the recess forming this channel to the adjacent section of the same pipe.

DESCRIPTION OF THE DRAWING These and additional features of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying drawing, in which FIG. 1 shows a plan view of one of the two plates forming a rib;

FIG. 2 shown a cross section which is taken along the line II II of FIG. 3 of an individual ribbed heating P p FIG. 3 shows a longitudinal section of the same pipe, which is taken along the line III III of FIG. 2;

FIGS. 3 to 6 show diagrammatic cross sections of the most essential parts of the apparatus for producing a ribbed pipe according to FIGS. 2 and 3 and illustrate three steps of the method of production of such a pipe;

FIGS. 7 and 8 show diagrammatic cross sections of two ribbed heating pipes each of which is provided with a core pipe of an oval cross section;

FIGS. 9 to II show diagrammatic cross sections of three pipe combinations each of which consists of three parallel core pipes which are connected to each other by pairs of rib plates;

FIG. 12 shows a cross section which is taken along the line XII XII of FIG. 13 of a ribbed pipe which is provided with cast-on fins or finlike projections;

FIG. 13 shows a longitudinal section of this pipe which is taken along the line XIII XIII of FIG. 12;

FIGS. 14 and 15 show longitudinal sections of a core pipe and a pipe jacket which are connected to each other by rectangular screw threads and are illustrated in their relative positions at room temperature and when heated;

FIG. 16 shows a plan view of a rib plate for a heating unit which is composed of a plurality of parallel flat ribbed pipes;

FIG. 17 shows a cross section of the flat core pipes for such a heating unit;

FIG. 18 shows a plan view of a removable spacing strip for the heating unit according to FIGS. I6 and 17;

FIG. 19 shows a longitudinal section of an assembling plate for assembling the pipe unit;

FIG. 20 shows a cross section of the assembled pipe unit, as seen in a direction vertical to the plane of FIGS. 16 to 18, and parts of which are enlarged for better demonstration; while FIGS. 21 to 24 illustrate similar to FIGS. 16, I7 20 and 21, the different parts of a futher modification of the invention.

SPECIFIC DESCRIPTION As illustrated in FIGS. 1 to 3 of the drawings, a ribbed heating pipe according to the invention comprises a plurality of pairs of equally shaped (identical) flat rectangular plates 1 which are to be secured at suitable distances from each other to a core pipe 2 so as to project radially therefrom and form heating ribs thereon. The two plates I of each pair are placed in alignment and abutting engagement with each other and each of the abutting sides or edges of the two plates is provided with a semicircular recess 3 of a diameter D which corresponds to the outer diameter D of the core pipe 2, as shown in FIGS. 2 and 3, and each of these recesses 3 is provided with a central groove 5 of a dovetailed shape and two lateral grooves 6 of a substantially semicircular shape. Each of these grooves 5 and 6 has a relatively shallow depth 1.

A plurality of these pairs of rib plates 1 when combined with a core pipe 2 form a ribbed pipe 7, a short section of which is illustrated in FIG. 3. For securing each pair of these rib plates 1 to the core pipe 2, the

edges 4 of their recesses 3 are applied against the outer surface of the core pipe 2 and a suitable metal 9, for example, aluminum, is cast between the adjacent pairs of plates it around the core pipe 2 so that, when cooled, a shell or jacket will be formed tightly around and in heat-conductive engagement with each of the adjacent sections of the outer pipe surface 8 between the rib plates 1. The mold which is required for this casting process is additionally provided with annular grooves at both sides of the rib plates 1 so that the liquid metal 9 will also penetrate through these grooves and also form small annular flanges (Beads) 11 at both sides of each plate 1 in which the edges 4 of the recesses 3 are embedded. The metal 9 then also fills out the grooves 5 and 6 in plates 1 and thus connects the adjacent sections 3.3 of jacket 1t) integrally with each other.

FIGS. 4 to 6 illustrate three successive steps in carrying out the casting operation by means of a mold 14. This mold essentially comprises two equal mold sections 15 each of which is provided with a trough-shaped recess 16. When the mold sections 15 abut against each other, these two recesses 16 together form a continuous longitudinal channel 17 containing the core pipe 2. Both mold sections 15 are further provided with a plurality of transverse slots 18 which are spaced from each other at the distances at which the rib plates 1 are to be spaced from each other. On both sides of each of these mold sections 15, framelike supporting members 20 are provided which serve as supports for the rib plates 1 and are provided with inner guide slots 19 into which the rib plates 1 may be inserted.

At the beginning of the casting operation, the two mold sections 15 are at first moved toward the core pipe 2 in the manner as illustrated in FIG. 4, so that this pipe 2 will be located within the channel 17. After the rib plates 1 which are to be secured to the core pipe 2 have also been inserted into the supporting members 29, these rib plates 1 which are thus combined with each other into a set are pushed by means of press plungers 21 at both sides of frame members 20 so far in the direction of the arrows 22 into the transverse slots 18 of the mold sections 15 until the edges 4 of the recesses 3 of rib plates 1 abut tightly against the outer surface 8 of the core pipe 2. As may be seen particularly in FIG. 5, rib plates 1 are held in this position by the press plungers 21 so that the casting operation may then be carried out. During this casting operation, liquid metal, preferably aluminum, is injected through the longitudinal channel 23 in the lower part of mold l4 and from this channel 23 through the different cross channels 241. This metal when cooled connects the rib plates 1 and the core pipe 2 securely to each other in the manner as previously described in detail.

When the casting metal has cooled, the two mold sections 15 are at first drawn only slightly away from each other so as to insure that the solidified metal will properly separated from the walls of the mold. Thereafter, the two mold sections 15 are pulled fully away from such other to the position as shown in FIG. 6, and they will then also take along the supporting members 20 and the press plungers 21. The completed ribbed pipe 7 may then be removed from the mold 14 or it may be shifted in the mold in a direction vertical to the plane of the drawing for being provided with further ribs. As soon as a new core pipe 2 has been shifted longitudinally for being provided with further ribs, the mold sections 15 and also the supporting members 20 are moved to their starting positions as shown in FIG. 4, so that a new casting operation may thereafter be carried out.

FIGS. 7 and 8 illustrate diagrammatically individual ribbed pipes 25 each of which has a core pipe 26 of an elliptical cross section. The walls of the recesses 27 in the rib plates 1 which are shaped so as to fit tightly around the core pipe 26 are also in these cases provided with grooves 28 of any suitable shape which in the subsequent casting operation are filled out with the casting metal to connect the adjacent jacket sections to each other.

Each of FIGS. 9 to 11 illustrates a pipe unit 29 which is composed of three parallel core pipes 30, 31 and 32, respectively, which are connected to each other by pairs of rib plates 1. Core pipes 30 have a circular cross section, core pipes 31 have a drop-shaped cross section, and core pipes 32 have an elliptical cross section. The walls of the recesses 27 in each pair of rib plates 1 are again provided with suitable grooves 28. These pipe units 29 are produced in the same manner as the individual ribbed pipes as previously described and their rib plates 1 are likewise secured to the core pipes 30 to 32, respectively, by a casting metal 9.

FIGS. 12 and i3 illustrate a ribbed pipe 23 which is similar to the ribbed pipe 7 as shown in FIGS. 2 to 3 and again comprises a core pipe 2 to which pairs of rib plates 1 are secured. The two mold sections 15 for producing this ribbed pipe 33 are, however, provided with additional recesses to permit short fins 34 to be cast on each of the rib plates 1, as illustrated in cross section in the upper part of FIG. 13. Furthermore, in addition to the grooves 5 and 6 in each pair of rib plates 1, the adjacent edges 35 of the two plates are also provided with dovetailed recesses 36 through which the casting metal 9 penetrates during the casting operation in the manner as indicated in FIGS. 12 and 13 so as to form webs 37 which connect the fins 34 on both sides of each rib plate 1 securely to each other.

Instead of such short fins 34 on each rib plate 1, it is also possible to cast continuous fins 38 on the rib plates 1 which then connect the adjacent plates 1 to each other in the manner as illustrated in the lower part of FIG. 13. The recesses 36 in each pair of rib plates 1 are also in this case filled out with casting metal 9 so that the webs 37 which are then formed connect the individual fins 38 to each other.

In order to attain a very secure and highly heat-conductive connection between the core pipe 2 and the jacket 14), it is of advantage to cut a screw thread 39 into the outer wall 8 of the core pipe 2. This screw thread 39 has a square or rectangular cross section so that its heated flanks d0 extend at right angles to the longitudinal axis of pipe 2. While the core pipe 2 is made of steel, cast iron or the like, the jacket 10 consists of aluminum which has a thermal coefficient of expansion approximately twice as high as that of steel. When this jacket 10 after being cast has cooled to room temperature, it will be tightly shrunk upon the core pipe 2 and its material will be subjected to a tensile stress up to its yield point. If, for example, the core pipe 2 together with the jacket 10 is then heatd to a temperature of, for example, 300 C., jacket 16 will expand considerably more than the core pipe 2 and, despite its initial tension which prevails at room temperature, its diameter will increase and it will therefore separate slightly from the core pipe 2 in the manner as indicated in FIG. 15. However, since the screw thread 39 is cut into the outer wall surface 8 of core pipe 2, there will still be an uninterrupted heat conduction between the core pipe 2 and the jacket 10 due to the engagement of the vertical flanks of the screw thread 39 of core pipe 2 with the corresponding vertical flanks 40 of the jacket 10. This uninterrupted heat conduction is, however, fully attainable only, despite the increase in the inner diameter of jacket 10, if the flanks 40 of the screw threads of pipe 2 and thus also the corresponding flanks 41 of the jacket 10 extend at approximately right angles to the longitudinal axis of the core pipe 2. If the flanks 40 and 41 of the screw threads would be made at considerably smaller angles, they would at least slightly separate from each other.

FIGS. 16 to 20 illustrate diagrammatically the mode of production of a heating unit which consists of a plurality of flat pipes which are provided with ribs which may be spaced at a very short distance, and as little as about 1 mm, from each other. The individual rib plates 42, one of which is shown in FIG. 16, may be punched, for example, out of sheet aluminum and be provided with transverse slots 43 into which the individual flat pipes 44 of a set 45 of such pipes, as shown in FIG. 17, are to be inserted. The edges of these transverse slots 43 are again provided with small recesses 6 through which the liquid metal 9 will penetrate during the subsequent casting operation.

In order to insure that the individual rib plates 42 will be uniformly spaced from each other, spacing strips 46, as shown in F 1G. 18, are inserted between the rib plates 42 during the assembly of the pipe unit. These spacing strips 46 which are preferably punched out of sheets of asbestos, cardboard or the like have a thickness s which corresponds to the distance between the adjacent rib plates 42. They are also provided with transverse slots 47 of a width b which is at least equal to the distance a between the opposite edges of the recesses 6 in the edges of the transverse slots 43 of rib plates 42, as shown in FlG. 16. Furthermore, the edge 48 of each of these spacing strips 46 is also provided with recesses 49 which are offset in the longitudinal direction of the strip relative to the transverse slots 47 and have a dovetailed shape. The bottom edge of each of these dovetailed recesses 49 is further provided with a central groove 54 For assembling the rib plates 42 with the spacing strips 46 and connecting them to each other, an assembling plate 51 is employed, as shown in cross section in FIG. 19. This assembling plate is provided with supporting ribs 52 of a dovetailed cross section, and each of these ribs 52 is provided with a central projecting ridge 53. The cross-sectional shape of the ribs 52 including the ridges 53 corresponds to that of the recesses 49 and in the spacing strips 46.

FIG. 20 finally illustrates the manner in which the flat-pipe heating unit is assembled. At first, the required number of rib plates 42 and intermediate spacing strips 46 are stacked on each other so that the transverse slots 43 and 47 will be in alignment with each other. The entire stack may then be held together by the supporting ribs 52 on the assembling plate 51 which engage into the corresponding recesses 49 in the spacing strips 46. The projecting ridges 53 on ribs 52 then engage into the grooves 50 of the spacing strips 46 and also into corresponding grooves 55 which are provided in the edges 54 of the rib plates 42 and thus prevent the rib plates 42 from shifting relative to each other and to the spacing strips 46. The supporting ribs 52 and their projecting ridges 53 on the assembling plate 51 may be either inserted into the corresponding recesses of the complete stack of rib plates 42 and spacing strips 46 or the rib plates and spacing strips may be stacked upon each other on the assembling plate 51.

When the rib plates 42 and the spacing strips 46 have thus been combined into a stack as shown in FIG. 20, the individual flat pipes 44 are inserted into the recesses 56 of the stack which are formed by the slots 43 and 47 either by being inserted laterally through the open ends of these recesses or by being passed into the latter from above. Due to the provision of the opposite grooves 6 in the lateral edges of the transverse slots 43 of rib plates 42 and due to the greater width b of the transverse slots 47 in the spacing strips 46, narrow channels 57 are formed at both sides of each pipe 44 which permit the pipes 44 to be embedded in the casting metal 9 during the subsequent casting operation and will then be filled out completely with this metal, whereby the individual rib plates 42 will be likewise embedded in the casting metal and firmly secured to the pipes 44. When the casting metal 9 has solidified, the entire row of spacing strips 46 on the supporting ribs 52 of the assembling plate 51 is withdrawn by the latter from the unit consisting of the pipes 44 and the rib plates 42.

When employing cardboard, asbestos sheets or the like, for producing the spacing strips 46, these strips and the rib plates 42 are preferably punched out on separate machines both of which operate at the same speed although their operations are offset at a half cycle relative to each other so that by means of a combined discharge device the punched rib plates 42 and spacing strips 46 may be automatically stacked on each other and fitted on the supporting ribs 52 of the assembling plate 51.

If the spacing strips 46 consist of cardboard or the like the rib plates 42 may also be properly aligned with each other in the stacking process by employing an adhesive instead of mounting them on an assembling plate 51. This adhesive should, however, have the property that it loses its adhesive or binding power completely when the liquid metal 9 has been cast into the stack, for example, due to being heated by the liquid metal 9, so that when the casting operation is completed and the casting metal 9 has cooled, the spacing strips 46 may again be easily withdrawn from the rib plates 42.

FIGS. 21-to 24 show an embodiment of the invention which is somewhat similar to that as shown in FIGS. 16, 17, 19 and 2t and is especially suitable for the manufacture of an engine radiator for an automobile. The individual parts of these two embodiments which are similar to each other are designated by the same reference numerals. Instead of employing separate spacing strips 46 as shown in FIG. 18 which separate the adjacent rib plates 42 of the stack fromeach other at a distance s and are removable after the casting operation, this further embodiment of the invention is provided with spacing tabs 58 of a dovetailed shape which are partly punched out of the rib plates 42 in the manner as shown in FIGS. 21 and 24 and are bent over at right angles about the shorter edges 59 of the tabs so that the outer cut edge 60 of each tab 58 abuts against the shorter edge 59 of the adjacent rib plate 42 of the stack without engaging into the aperture 61 of this adjacent plate, which is formed by cutting out and bending over each tab 58.

In order to prevent the casting metal from penetrating into the channels 62 between the adjacent rib plates 42, these rib plates 42 are bent closely adjacent to the edge portions 64 in which the slots 43 are provided into which the flat pipes 44 are to be inserted, so that the parts of each rib plate adjacent to the slots 43 have a zshaped cross section, as shown in FIGS. 21 and 24. Of course, instead of providing flat pipes 44 as shown in FIGS. 17 and 22, it is also possible to insert a plurality of parallel pipes of a circular cross section into each slot 43 of the rib plates.

After the rib plates 42 are stamped out and bent as described and their tabs 58 are also bent over, they may be stacked on each other in the manner as shown in FIG. 24, so that the z-shaped parts 63 and also the tabs 58 of the adjacent rib plates support each other, respectively. The inner sides of each pair of these 2- shaped parts 63 which are separated by a slot 44 into which a flat pipe 44 or a series of parallel pipes 65 are inserted then form an open casting channel 66 through which the casting metal may be poured.

The operation of stacking the rib plates 42 so as to be in proper alignment with each other may be carried out by the aid of a common assembling plate 67, as shown in FlG. 23, which is provided with projections 68 which engage into corresponding recesses 70 in the edges 69 of the rib plates 42 andprevent the latter from shifting relative to each other. If desired, this assembling plate 67 may also be provided with casting channels (not shown) which communicate with the casting channels 66 through which the liquid metal may be cast into the latter. Since the material of the rib plates 42 is very thin, it is advisable to support their z-shaped webs 63 during the casting operation by filling out the channels 62 between the adjacent rib plates with fine sand which may again be easily removed when the casting operation is completed.

If the adjacent rib plates 1 of the embodiments according to the invention as illustrated in FIGS. 2 and 3 and 7 to 13 are to be spaced at short distances from each other, the rib plates 1 may likewise be provided with spacing tabs 58 similarly as described with reference to FIGS. 21 and 24 and as indicated in dotted lines in FIG. 1.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, 1 wish to have it understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

l. A heat-exchanger structure comprising a metallic core tube; a multi licit of tallic fin lates aced along said tube andforrfied w i fh openmgs compi mentary to and of approximately the same outer dimensions of said tube whereby the walls of said openings closely hug the outer surface of said tube and are perpendicular thereto, said plates being formed with recesses along said walls spaced about the periphery of said tube and open in the direction thereof; and a sheath of cast metal surrounding said tube between said plates and extending monolithically through said recesses on opposite sides of each plate while lying against opposite faces of each plate along the walls thereof, said cast metal filling said recesses and forming a bead along each of said faces.

2. The structure defined in claim 1 wherein said sheath is unitarily and monolithically formed with at least one radially projecting rib between said plates.

3. The structure defined in claim 2 wherein each of said plates comprises a pair of plate halves lying in a common plane and defining a junction line between the halves.

4. The structure defined in claim 3 wherein the plate halves of each plate are formed with dovetail cutouts opening toward the respective line, the cast metal of said rib filling said cutouts.

5. The structure defined in claim 1 wherein a plurality of such tubes traverses each of said plates and is surrounded by a respective said sheath.

6. The structure defined in claim 1 wherein said recesses are of outwardly widening dovetail configuratron.

7. The structure defined in claim 1 wherein said tube has a flattened cross section.

8. The structure defined in claim 1 wherein said tube has a generally polygonal cross section. 

1. A heat-exchanger structure comprising a metallic core tube; a multiplicity of metallic fin plates spaced along said tube and formed with openings complementary to and of approximately the same outer dimensiOns of said tube whereby the walls of said openings closely hug the outer surface of said tube and are perpendicular thereto, said plates being formed with recesses along said walls spaced about the periphery of said tube and open in the direction thereof; and a sheath of cast metal surrounding said tube between said plates and extending monolithically through said recesses on opposite sides of each plate while lying against opposite faces of each plate along the walls thereof, said cast metal filling said recesses and forming a bead along each of said faces.
 2. The structure defined in claim 1 wherein said sheath is unitarily and monolithically formed with at least one radially projecting rib between said plates.
 3. The structure defined in claim 2 wherein each of said plates comprises a pair of plate halves lying in a common plane and defining a junction line between the halves.
 4. The structure defined in claim 3 wherein the plate halves of each plate are formed with dovetail cutouts opening toward the respective line, the cast metal of said rib filling said cutouts.
 5. The structure defined in claim 1 wherein a plurality of such tubes traverses each of said plates and is surrounded by a respective said sheath.
 6. The structure defined in claim 1 wherein said recesses are of outwardly widening dovetail configuration.
 7. The structure defined in claim 1 wherein said tube has a flattened cross section.
 8. The structure defined in claim 1 wherein said tube has a generally polygonal cross section. 